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Air Quality Monitor (CO2, Temp, RH, Pressure) ***Drivers attached*** - Page 2 — Parallax Forums

Air Quality Monitor (CO2, Temp, RH, Pressure) ***Drivers attached***

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,319
    edited 2022-05-30 19:16

    I'd suggest you add a connection from Prop p6 to DS1307 pin 7, with a high ohms pullup. The 1 second heartbeat from the RTC can be useful.

    That's a nice thought. I'm going to put it off for now, though, until I know for sure that the SPS30 will work well on the I2C bus. If it doesn't, I'll need P6 and P7 for SDA and SCL, so I can use P4 and P5 for serial comms.

    The JST cable, at least, is discrete-wire, rather than closely-abutted ribbon conductors. So crosstalk should be less of an issue. And I'm using 4.7K pull-ups. Still, for a 3.3V Vdd, 3.3K pull-ups would be even better. The original I2C spec that called for 4.7K pull-ups was written for a 5V Vdd. To get the same initial pull-up current at 3.3V, you need 3.3K.

    -Phil

  • Very interesting project I would be interested in buying a couple of them when you are done with all of the revisions on the circuit board

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